Interview Questions and Answers for 'Uri' | Search Interview Question

Interview Questions and Answers for 'Uri' - 36 question(s) found - Order By Newest

Advanced level question. Frequently asked in High end product companies. Frequently asked in Google , Cognizant and Deloitte ( Based on 2 feedback )

Q1. Why is String immutable in Java ?

Core Java

Ans. 1. String Pool - When a string is created and if it exists in the pool, the reference of the existing string will be returned instead of creating a new object. If string is not immutable, changing the string with one reference will lead to the wrong value for the other references.

Example -

String str1 = "String1";
String str2 = "String1"; // It doesn't create a new String and rather reuses the string literal from pool

// Now both str1 and str2 pointing to same string object in pool, changing str1 will change it for str2 too

2. To Cache its Hashcode - If string is not immutable, One can change its hashcode and hence it's not fit to be cached.

3. Security - String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment.

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Q2. Explain OOPs

or

Explain OOPs Principles

or

Explain OOPs Concepts

or

Explain OOPs features

or

Tell me something about OOPs

Core Java

Ans. OOPs or Object Oriented Programming is a Programming model which is organized around Objects instead of processes. Instead of a process calling series of processes, this model stresses on communication between objects. Objects that all self sustained, provide security by encapsulating it's members and providing abstracted interfaces over the functions it performs. OOP's facilitate the following features

1. Inheritance for Code Reuse
2. Abstraction for modularity, maintenance and agility
3. Encapsulation for security and protection
4. Polymorphism for flexibility and interfacing

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Frequently asked in all types of companies especially Indian Services companies. Frequently asked in CTS (Based on 2 feedback)

Q3. What is the use of hashcode in Java ?

Core Java

Ans. Hashcode is used for bucketing in Hash implementations like HashMap, HashTable, HashSet etc. The value received from hashcode() is used as bucket number for storing elements. This bucket number is the address of the element inside the set/map. when you do contains() then it will take the hashcode of the element, then look for the bucket where hashcode points to and if more than 1 element is found in the same bucket (multiple objects can have the same hashcode) then it uses the equals() method to evaluate if object are equal, and then decide if contain() is true or false, or decide if element could be added in the set or not.

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Q4. How does making string as immutable helps with securing information ? How does String Pool pose a security threat ?

Core Java

Ans. String is widely used as parameter for many java classes, e.g. network connection, opening files, etc. Making it mutable might possess threats due to interception by the other code segment or hacker over internet.

Once a String constant is created in Java , it stays in string constant pool until garbage collected and hence stays there much longer than what's needed. Any unauthorized access to string Pool pose a threat of exposing these values.

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Advanced level question usually asked to senior developers , leads and architects.

Q5. How does volatile affect code optimization by compiler?

Core Java

Ans. Volatile is an instruction that the variables can be accessed by multiple threads and hence shouldn't be cached. As volatile variables are never cached and hence their retrieval cannot be optimized.

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Q6. How to find whether a given integer is odd or even without use of modulus operator in java?

Core Java

Ans. public static void main(String ar[])
{
int n=5;
if((n/2)*2==n)
{
System.out.println("Even Number ");
}
else
{
System.out.println("Odd Number ");
}
}

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Q7. What is a ConcurrentHashMap ?

Core Java

Ans. ConcurrentHashMap is a hashMap that allows concurrent modifications from multiple threads as there can be multiple locks on the same hashmap.

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Q8. Can a EC2 instance have multiple Security Groups ? Can a single security group be assigned to multiple Ec2 instances ? If either of them is true , doesn't it result in conflict ?

Amazon Web Services (AWS)

Ans. We can assign multiple security groups to single instance and we can use single security group with multiple instances.

It never results in conflict as security groups only have allow rules and no deny rules. Multiple security groups for an instance results in union of all rules.

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Q9. Can we deny access for particular IP using Security Groups ?

Amazon Web Services (AWS)

Ans. No, We can do that through ACL

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Q10. What is a Webdriver ?

Testing

Ans. Selenium WebDriver is a tool for automating web application testing.It helps in replicating the manual tester behavior like keyboard entry, mouse events etc and then matching the output against the expected.

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Q11. Java doesn't provide exclusive access to memory like C/C++ and other lower level languages ? What are the advantanges and disadvantages ?

Core Java

Ans. Yes, doesn't provide exclusive access as we cannot allocate and deallocate memory exclusively as Java internally manages it. The advantage of this is that it relieves the coder for such tasks and helps protect from many bugs that may get introduced with imperfect coding. Moreover as java garbage collector collects all unclaimed memory or objects, it helps the application from memory leaks.

On the flip side , as coder doesn't have extensive excess to memory , it is upto java to decide on the state for programming construct and data storage and hence may introduce some security risks. For example - Java keeps string literals in string pool and there is no exclusive way to remove it and hence may stay and sensitive data in string pool may introduce security issues. Moreover when we overwrite a value or object for a variable / reference, it is upto java to purge those values and hence it may stay in memory for a while till java decide that it is no longer referenced and hence should be removed and hence makes it vulnerable for inappropriate access.

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Q12. What are the types of authentication used in Web services ?

Web Service

Ans. Encrypted User Name / Password
Encrypted Password within Cookie
Encrypted Tokens
IP
Client Certificates
Oauth

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Q13. How have you configured Security Groups ?

Amazon Web Services (AWS)

Ans. AWS console >> security groups >> Create security group >> Configure security group bases on Network requirement of EC2 instance

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Q14. Describe best practices with respect to AWS security groups ?

Amazon Web Services (AWS)

Ans. Configure it while creating EC2 instance only

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Q15. Have you ever heard about csrf attacks ?

Security

Ans. Yes, Cross-Site Request Forgery (CSRF) is an attack that forces an end user to execute unwanted actions on a web application in which they're currently authenticated.

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Q16. Do you think a csrf token should only be generated after authentication ?

Security

Ans. No, they should be created before authentication too

https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.html#login-csrf

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Usually asked only to fresh graduates and less experienced developers.

Q17. What is a daemon thread? Give an Example ?

Ans. These are threads that normally run at a low priority and provide a basic service to a program or programs when activity on a machine is reduced. garbage collector thread is daemon thread.

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Q18. What is unmarshalling ?

Ans. Its the process of creating Java Objects out of XML structures.

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Q19. What is the difference between URI, URL and URN ?

Java EE

Ans. URI stands for Uniform Resource Indicator
URL stands for Uniform Resource Locator
URN stands for Uniform Resource Name

URI = URL + URN

For ex - http://javasearch.buggybread.com/InterviewQuestions/questionSearch.php?keyword=url

This is URI. The string from start till .php is URL whereas keyword=url is URN.

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Q20. What is a certificate authority ?

Security

Ans. A trusted organization which issues public key certificates and provides identification to the bearer.

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Q21. What is ACL ?

Operating System

Ans. Access Control List or ACL is the list of permissions attached to an object in the File System.

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Q22. What is meant by the statement "Java is turing complete" ?

Core Java

^{This question is still unanswered. Can you please provide an answer.}

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Q23. Can you tell something about Web security ?

Web

^{This question was recently asked at 'Symantec'.This question is still unanswered. Can you please provide an answer.}

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Q24. Have you ever changed IAM policy ?

Amazon Web Services (AWS)

Ans. Yes I did it for an execution role of a Lambda function to give it write access on S3 bucket.

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Q25. What is DDOS attack ?

Security

Ans. DDOS is denial of service attack in which the hacker seeks to make a machine or resource unavailable to its expected users by disrupting services.

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Q26. What is XSS or Cross site scripting ?

Security

Ans. XSS or cross site scripting is a javascript vulnerability in web applications. The easiest way to explain this is with a case when the user enters a script in the client side input fields and that input gets processed without getting validated. This leads to untrusted data getting saved and executed on the client side.

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Q27. Which IAM policy condition key should be used if you want to check whether the request was sent using SSL?

Amazon Web Services (AWS)

Ans. AWS: secure transport

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Q28. If you are asked to develop a financial system, how would you make sure that there are proper checks , balances and audits ?

Solution

^{This question was recently asked at 'BzzAgent'.This question is still unanswered. Can you please provide an answer.}

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Q29. What are the ways we can get over XSS or cross site scripting vulnerability ?

Security

Ans. The counter measures of XSS are input validation and implementing a CSP (Content Security Policy).

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Q30. How can an XSS attack harm a system ?

Security

^{This question is still unanswered. Can you please provide an answer.}

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